Various methods have been employed for years to secure items of personal property, bicycles, motorcycles and similar vehicles against theft. With the particular current interest in bicycles as well as technological advances in materials and components, bicycles are becoming more sophisticated and more expensive, some costing many hundreds to several thousands of dollars each. The problem of bicycle and motorcycle theft is exacerbated by the light weight and portability of the vehicles. U.S. Pat. No. 5,408,212 issued to Meyers et al. ("the Meyers' patent") combines several recent schemes for preventing bicycle theft. The Meyers' patent also contains a good description of the state-of-the-art of bicycle anti-theft devices, and is incorporated by reference herein.
The "U" lock is widely used as a mechanical deterrent to theft by virtue of its strength. Such locks are used to lock the vehicle frame to a permanent or fixed object. Great force is needed to cut through or break a "U" lock. In the Meyers' patent, a cable with conductive core is utilized as a second means of theft deterrent. When the circuit created by the cable is broken, an alarm sounds either alerting the bicycle owner of an attempted theft, or scaring the thief away by drawing attention to the vehicle.
The Meyers' patent provides yet another mode of protection in that a motion sensor may be set to detect any movement of the bicycle and again, triggers an alarm upon such detection. Such schemes are flawed in that in the case of bicycles, many times while secured in a location with the owner away, the bicycle may be subject to motion by various causes. For example, other riders securing their bicycles may bump the bicycle, or wind may affect the stability of the bicycle. Such influences often trigger the alarm, thereby wasting precious battery power and increasing the possibility that when an actual attempt to take the bicycle is made, no power is left to sound the alarm when really needed.
Other alarms also utilize circuitry which detects discontinuity when the cable of the lock is cut. The drawback to such an alarm is that typically, the alarm does not sound until the cable is cut, and at such a point, the bicycle is already free to be placed in a truck or such vehicle, particularly since a bicycle or motorcycle can be spirited away in less than 1 minute. In many cases, bicycle thieves are petty thieves who cut the cable and ride away on the stolen bicycle. The unwanted attention of an alarm which is activated before the bicycle is set free of its locking cable, particularly when the alarm is securely fixed to the bicycle so that the alarm continues to sound whether the bicycle is ridden away or put into the bed of a pickup truck or other vehicle, constitutes a serious deterrent to theft.
What is needed then, is an anti-theft device with an alarm sensitive cable which is easily replaceable, and which does not have an easily overridden audible alarm. Further, an alarm is needed which detects the initial attempt to cut the cable, sounding the alarm before the bicycle can be spirited away, and moreover, which may reside on the bicycle, keeping the attention of a passersby as the bicycle is moved.
In the prior art, represented by the Meyers' patent, once the locking cable is cut, it is very often not easily replaceable. Also, cables such as those in the Meyers' patent may be defeated by short-circuiting the cable. Such a propensity for getting around the main security means of a locking device renders such a device vulnerable to educated thieves. What is needed then is a circuitry which does not allow subversion by means such as short-circuiting.
The known prior art also involves various schemes to indicate that a system is armed, sometimes without a circuit being armed, but just employing a visual indication of activation to ward off potential thieves. However, professional thieves quickly become acquainted with such products in the market so that fake alarms may be easily recognized, and therefore, ignored. What is needed is both an indication for potential thieves as well as the vehicle owner that a system is real, functioning, and having plenty of power.
The problem with many such indications manifests itself as a constant drain on the power source. A particularly ironic scenario involves an alarm system which is deprived of power by passive systems such that when called upon to sound an alarm, the battery dies during a portion of the alarm duration, or dies altogether, never allowing the alarm to sound at all. What is needed then is a means of conserving power without compromising the detection ability or annunciation intensity of the anti-theft device. Such an anti-theft device can be adapted to a variety of applications, like expensive instruments, costly computers or electronic equipment, and the like.